Streptococcus thermophilus

Streptococcus thermophilus is a lactic acid bacterium used as a starter culture in yogurt and many cheeses. It ferments lactose into lactic acid, helping acidify milk and shape dairy products’ texture and flavor.

Lactose fermentation: The anaerobic conversion of lactose into fermentation products, often including lactic acid. It supplies the lactic acid that lowers milk’s pH during fermentation.
Yogurt: A fermented milk food produced by bacterial acidification and coagulation. S. thermophilus is one of the characteristic starter organisms used to make it.
Streptococcus: A genus of spherical, Gram-positive bacteria that commonly grow in chains or pairs. S. thermophilus is one species within this bacterial genus.
Streptococcus pyogenes: A human-adapted bacterium that causes diseases including strep throat and scarlet fever. Unlike this pathogen, S. thermophilus is chiefly associated with food fermentation.
Lactic acid bacteria: A broad group of bacteria that produce lactic acid during carbohydrate fermentation. S. thermophilus belongs to this functional group of fermenting bacteria.
Cheese: A family of foods made by coagulating milk and separating curds from whey. The bacterium acidifies milk in the production of many cheese varieties.
Gram-positive bacteria: Bacteria whose cell walls retain crystal violet stain because of a thick peptidoglycan layer. S. thermophilus has the characteristic Gram-positive cell-wall structure.
Streptococcus pneumoniae: A bacterium that can cause pneumonia, meningitis, and other infections. Its major clinical role contrasts with S. thermophilus’s established use in dairy.
Lactobacillus delbrueckii subsp. bulgaricus: A lactic acid bacterium commonly paired with S. thermophilus in yogurt cultures. The two organisms exchange growth-promoting compounds and jointly acidify yogurt.
Starter culture: A selected population of microorganisms added to food to drive controlled fermentation. Dairy producers use S. thermophilus strains to initiate predictable acidification.

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